1. Field of the Invention
The present invention relates to semiconductor manufacturing. More particularly, the present invention relates to electrical beam inspection for semiconductor manufacturing.
2. Description of the Background Art
Automated inspection and review systems are important in process control and yield management for the semiconductor and related microelectronics industries. Such systems include optical and electron beam (e-beam) based systems.
Despite recent advances in electron beam inspection and review, further improvement may be made. For example, it is typically desirable to increase the resolution of an inspection or review system. Resolution may be defined as the smallest distance apart that two point may be distinguishable as separate points. Current e-beam inspection and review systems have resolutions of typically about 100 nanometers (0.1 micrometers). Generally, the higher the resolution, the smaller the defects that may be detected and characterized by the automated inspection and review systems. In other words, the resolution of an e-beam system limits the smallness of the features that may be detected and characterized. Hence, in order to detect and characterize smaller and smaller features on semiconductors and other specimens, it is desirable to increase the achievable resolution of the system.
E-beam inspection and review systems typically operate by scanning an incident (primary) electron beam over an area of a specimen being examined. One factor influencing resolution of such an e-beam inspection or review system is the spot size of the incident electron beam. Generally speaking, the smaller the spot size, the higher the achievable resolution. Hence, it is desirable to reduce the spot size of the incident electron beam.
Unfortunately, reducing the spot size often leads to the disadvantage of a lower beam current. A lower beam current is undesirable as it increases the time needed to image a specimen being inspected or reviewed. This results in a lower throughput for the system.
What is needed is a way to decrease the spot size of the incident electron beam in an e-beam inspection or review system without a corresponding decrease in the beam current. In other words, it is desirable to generate a primary electron beam with both a small spot size and a high beam current for use in an e-beam inspection or review system.